After studying stool samples from more than 1,300 cancer patients, scientists discovered distinct gut microbiome patterns linked to different cancers.
Mayo Clinic researchers analyzed samples from 1,364 cancer patients across various cancer types, stages and treatments as part of the Mayo Clinic Cancer Microbiome Cohort study, published in Cell.
Scientists have discovered unique microbiological signatures associated with five major cancer groups, while identifying notable differences in patients diagnosed at younger ages.
One of the most striking findings involved early-onset colorectal and breast cancers, both of which have been increasing among young adults in recent years.
Patients aged 50 and younger with colorectal cancer had higher lactate levels and greater amounts of a bacteria called Veillonella parvula, which feeds on lactate.
Meanwhile, younger breast cancer patients showed changes in 64 bacterial species and lower levels of primary bile acids.
“We observed distinct changes in microbes and metabolites in early-onset breast and colorectal cancers, but not in brain cancer,” said Purna C. Kashyap, MBBS, a gastroenterologist at the Mayo Clinic. News week.
At this point, Kashyap said the findings don’t yet explain why breast and colorectal cancers are becoming more common among young adults.
“However, they provide potential biomarkers and mechanistic leads that can now be tested in independent clinical cohorts and in preclinical models,” he said.
In colorectal cancer, for example, tumors can produce high levels of lactate, potentially creating an environment conducive to the growth of V. parvula.
It is not yet known whether this relationship contributes to the development of cancer.
Beyond age-related differences, the team identified 341 bacterial species associated with five cancer groups after accounting for other health conditions.
Neuroendocrine tumors were linked to a loss of beneficial gut bacteria, while liver and intrahepatic bile duct cancers had higher levels of several microbes, including Enterococcus faecalis.
Distinct microbial profiles have also been observed in esophageal cancer, lymphocytic leukemia, and multiple myeloma.
The study also suggests that the microbiome could help predict which patients are most likely to experience treatment side effects.
Researchers found that among patients receiving the chemotherapy drug 5-fluorouracil (5-FU), those who later developed diarrhea tended to have lower levels of bacterial genes capable of breaking down the drug before treatment began.
The association was not found in patients receiving another chemotherapy drug, carboplatin.
Ruben Mars, Ph.D., assistant professor of medicine at the Mayo Clinic, said the findings raise the possibility that microbiome-based tests could one day help identify patients at greater risk of side effects from certain treatments.
“Importantly, we found a link between the microbiome and side effects of one chemotherapy drug, intravenous 5-fluorouracil, but not all chemotherapy drugs,” Mars said. News week.
Although the results could eventually support the development of a clinical test, he said researchers still need to validate the results in larger, more diverse groups of patients.
“Ultimately, prospective clinical studies will be needed to demonstrate that integrating microbiome information into clinical decision-making actually improves patient outcomes,” Mars said. “Despite this, I am cautiously optimistic that microbiome-based testing will begin to enter the clinic in the near future. »
Researchers also identified gut bacteria associated with survival outcomes in colorectal, hepatic, and intrahepatic bile duct, ovarian, and prostate cancers, as well as melanoma.
Raymond Chang, medical director of Meridian Medical and former physician at Memorial Sloan-Kettering Cancer Center, said the research highlights the growing importance of the gut microbiome in cancer care.
Chang, who was not involved in the study, said two findings particularly stood out: the link between specific bacterial species and patient survival, and the association between gut microbiome composition and treatment side effects such as diarrhea caused by 5-FU chemotherapy.
“These results not only highlight the importance of the gut microbiome in cancer, but could also lead to further research in which manipulation of the microbiome could lead to improved survival as well as reduced treatment toxicities,” Chang said.
Reference
Yang, L., Singh, V., Gawey, BJ, Sinnwell, JP, Johnson, S., Billings, EC, Van Gorp, TM, Harrington, JJ, Slama, MQ, Till, LM, Singh, M., Samineni, TR, Zhu, M., Kalari, KR, Farrugia, G., Chen, J., Mars, RAT, & Kashyap, PC (2026). Microbiome signatures linked to cancer and treatment adverse events in a real-world cohort. Cell. (online) doi:10.1016/j.cell.2026.09.009.
Contact Newsweek editors on this story: Kara Dolman and Emma Lee-Sang
Gn Health
